To filter fluids and/or gases of undesired contaminants, porous filters are used in enclosed housings to effectuate particulate contaminant removal. Whether by physical/mechanical entrapment or electrokinetic separation with the use of charge modifiers, particulate matter suspended in the fluid and/or gas is removed and retained by the filter material while the fluid phase flows freely out of the filter. Numerous filter assembly variations have been constructed to address a wide variety of applications such as those in the biological and agricultural industries as is well known in the art.
One particularly advantageous construction is the assembly of multiple stacked disc-shaped filters to improve filter function by, for example, using filter discs with different porosities to capture differently sized particulate matter in a cascading configuration from largest to smallest pore size, and/or to increase the overall filter surface area to which the fluid and/or gas is exposed. Numerous configurations of this particular filter construction have been produced. One such construction is disclosed in Patent No. WO0183077 (hereinafter “The '077 Patent”).
The '077 Patent is drawn to a stacked disc filter configuration with a series of supports bearing strategically placed knife seals to direct fluid flow through the encapsulated filter material as shown in FIGS. 2-9 of the '077 Patent. The '077 Patent improves upon prior filter support constructions by introducing upstream and downstream filter supports that replace lenticular (double convex) support structures with relatively flat or non-lenticular supports. In one disclosed embodiment, upstream supports are provided with knife seals along an inner edge and downstream supports are provided with knife seals along an outer edge so as to create a liquid tight seal between the filter media and the apparatus outlet. This construction directs fluid with particulate contaminants introduced into the filter apparatus towards and through the apparatus filter media before the resulting filtrate exits through the apparatus' outlet.
The filter support structures are configured to reduce the overall thickness of the structures relative to lenticular forms so as to increase the available space for filter media. The relatively flat supports are supposed to reduce warping and distortion of the supports common to lenticular designs that may impact filter media integrity. The generally circular supports are segmented with ribs that define, but also isolate one inter-rib space from another. This can lead to possible sedimentation buildup in one segment that may retard or prohibit fluid flow through the segment. To create space necessary for adequate fluid flow, corrugations, spacers or nubs are used to create gaps.
To create tight seals necessary for desired performance, the filter disc/filter support combinations are subjected to pressure directed along a longitudinal axis of the filter assembly to compress the filter media and supports together. To this end, a rod is secured through centrally located openings in each support and filter disc and anchored to end caps positioned at opposing ends of the stacked filter disc/filter support assembly. At least one end cap is forced onto the assembled filter disc/disc supports until a desired pressure is reached. The rod is then bonded to the end cap with any excess rod cut away. The centrally located openings of both the filter discs and disc supports perform dual functions. The compressed, combined openings function as a continuous fluid outlet and provide a passage for the apparatus' support rod. Alternative embodiments are described that incorporate the central rod with exterior bands, clamps, nets or adhesive bands to maintain component compression and spacing.
To enhance fluid flow through the assembly, a series of channel openings are formed in a perimeter of the upstream supports to allow the radial infusion of fluid into the filter assembly from the gap formed between the filter housing and filter assembly. The channel openings or gaps create a segmented perimeter rim as shown in FIG. 3B of the '077 Patent.
Although this configuration may provide improvements over prior filter assemblies, there are a number of deficiencies driven by the once novel construction. Although the flattened radial ribs may increase available filter media volume, the use of a segmented perimeter for the upstream support weakens the overall structure of the support. The open areas provide perimeter regions of unsupported filter media.
The means used to create the compressive force necessary to create the liquid tight seals also creates deficiencies previously unresolved. A large portion of the tubular channel formed by the orifices of the stacked filter discs and disc supports is occluded by the compression rod. This significantly reduces the volume of filtrate that may flow out of the filter assembly and possibly create back-flow pressure that could impede maximum flow rate.
The noted problem is further exacerbated by the absence of any fluid channels in the central ring of the downstream support shown in FIG. 3A of the '077 Patent. Filtrate that migrates through the filter media has to continue in a downwardly path in order to reach the filter apparatus outlet as the inner ring of the downstream support acts as a mechanical barrier. The filter supports must maintain fluid pathways between the flat surface areas of the filter media and the support to allow for fluid to flow to the apparatus' central aperture.
These are but some of the exemplary problems resultant of the described prior art filter assembly configuration. What is needed is a filter apparatus that provides channels for radial infusion of fluids and radial egress of filtrates through the filter apparatus without the need to maintain the structural integrity of the filter media so as to maintain a gap between the filter media and disc supports. What is further needed is a stacked disc filter apparatus that eliminates the need for a central rod to compress and secure multiple layers of filter discs. A yet further need is to enable modular stacks of filter discs to be assembled in an extended train without compromising the structural integrity of the individual discs. These and other objects of the disclosure will become apparent from a reading of the following summary and detailed description of the disclosure.